An aftertreatment system is associated with an engine system. The aftertreatment system is configured to treat and reduce oxides of nitrogen (NOx) present in an exhaust gas flow, prior to the exhaust gas flow exiting into the atmosphere. In order to reduce NOx, the aftertreatment system may include a reductant delivery module, a reductant injector, and a Selective Catalytic Reduction (SCR) module.
The reductant injector is configured to inject a reductant into the exhaust gas flowing through a mixing tube of the aftertreatment system. In order to achieve improved levels of NOx conversion, better flow distribution and mixing of the reductant with the exhaust gases must be achieved. A mixing element is affixed inside the mixing tube so that increased turbulence and improved distribution of the reductant within the exhaust gases may be achieved within a short length of the mixing tube.
However, sometimes the mixing element may provide a surface for the reductant particles to collect thereon, leading to formation of solid deposits. Deposit formation may in turn lead to increased back pressure on the engine and reduce an overall effectiveness of the mixing element. Further, the functioning of the aftertreatment system may be affected as well, causing a reduction in NOx conversion capability and increase in ammonia slip.
U.S. Pat. No. 8,272,777 describes a method for mixing an exhaust gas flow with a fluid in an exhaust gas pipe of an exhaust gas system, in which the fluid is injected by means of an injection device into the exhaust gas pipe. The exhaust gas flow is guided in the exhaust gas pipe in the area of the injection device in a direction of flow parallel to the exhaust gas pipe. The fluid is injected directly onto a deflection element which is arranged in the exhaust gas pipe in a central direction of injection which deviates from the direction of flow by an angle, wherein by means of at least one sheet metal part which is provided on the deflection element and which is raised at least partially at an angle with reference to the direction of flow, the exhaust gas flow is diverted with reference to the direction of flow from its direction of flow into a central direction of distribution.